path: root/gconvert.c

/* GLIB - Library of useful routines for C programming
 *
 * gconvert.c: Convert between character sets using iconv
 * Copyright Red Hat Inc., 2000
 * Authors: Havoc Pennington <hp@redhat.com>, Owen Taylor <otaylor@redhat.com
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include <iconv.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>

#include "glib.h"
#include "config.h"

#ifdef G_OS_WIN32
#include <windows.h>
#endif

#include "glibintl.h"

GQuark 
g_convert_error_quark()
{
  static GQuark quark;
  if (!quark)
    quark = g_quark_from_static_string ("g_convert_error");

  return quark;
}

#if defined(USE_LIBICONV) && !defined (_LIBICONV_H)
#error libiconv in use but included iconv.h not from libiconv
#endif
#if !defined(USE_LIBICONV) && defined (_LIBICONV_H)
#error libiconv not in use but included iconv.h is from libiconv
#endif

GIConv
g_iconv_open (const gchar  *to_codeset,
	      const gchar  *from_codeset)
{
  iconv_t cd = iconv_open (to_codeset, from_codeset);
  
  return (GIConv)cd;
}

size_t 
g_iconv (GIConv   converter,
	 gchar  **inbuf,
	 size_t  *inbytes_left,
	 gchar  **outbuf,
	 size_t  *outbytes_left)
{
  iconv_t cd = (iconv_t)converter;

  return iconv (cd, inbuf, inbytes_left, outbuf, outbytes_left);
}

gint
g_iconv_close (GIConv converter)
{
  iconv_t cd = (iconv_t)converter;

  return iconv_close (cd);
}

static GIConv
open_converter (const gchar *to_codeset,
                const gchar *from_codeset,
		GError     **error)
{
  GIConv cd = g_iconv_open (to_codeset, from_codeset);

  if (cd == (iconv_t) -1)
    {
      /* Something went wrong.  */
      if (errno == EINVAL)
        g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_NO_CONVERSION,
                     _("Conversion from character set `%s' to `%s' is not supported"),
                     from_codeset, to_codeset);
      else
        g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_FAILED,
                     _("Could not open converter from `%s' to `%s': %s"),
                     from_codeset, to_codeset, strerror (errno));
    }

  return cd;

}

/**
 * g_convert:
 * @str:           the string to convert
 * @len:           the length of the string
 * @to_codeset:    name of character set into which to convert @str
 * @from_codeset:  character set of @str.
 * @bytes_read:    location to store the number of bytes in the
 *                 input string that were successfully converted, or %NULL.
 *                 Even if the conversion was succesful, this may be 
 *                 less than len if there were partial characters
 *                 at the end of the input. If the error
 *                 G_CONVERT_ERROR_ILLEGAL_SEQUENCE occurs, the value
 *                 stored will the byte fofset after the last valid
 *                 input sequence.
 * @bytes_written: the stored in the output buffer (not including the
 *                 terminating nul.
 * @error:         location to store the error occuring, or %NULL to ignore
 *                 errors. Any of the errors in #GConvertError may occur.
 *
 * Convert a string from one character set to another.
 *
 * Return value: If the conversion was successful, a newly allocated
 *               NUL-terminated string, which must be freed with
 *               g_free. Otherwise %NULL and @error will be set.
 **/
gchar*
g_convert (const gchar *str,
           gint         len,
           const gchar *to_codeset,
           const gchar *from_codeset,
           gint        *bytes_read,
	   gint        *bytes_written,
	   GError     **error)
{
  gchar *dest;
  gchar *outp;
  const gchar *p;
  size_t inbytes_remaining;
  size_t outbytes_remaining;
  size_t err;
  GIConv cd;
  size_t outbuf_size;
  gboolean have_error = FALSE;
  
  g_return_val_if_fail (str != NULL, NULL);
  g_return_val_if_fail (to_codeset != NULL, NULL);
  g_return_val_if_fail (from_codeset != NULL, NULL);
     
  cd = open_converter (to_codeset, from_codeset, error);

  if (cd == (GIConv) -1)
    {
      if (bytes_read)
        *bytes_read = 0;
      
      if (bytes_written)
        *bytes_written = 0;
      
      return NULL;
    }

  if (len < 0)
    len = strlen (str);

  p = str;
  inbytes_remaining = len;

  /* Due to a GLIBC bug, round outbuf_size up to a multiple of 4 */
  /* + 1 for nul in case len == 1 */
  outbuf_size = ((len + 3) & ~3) + 1;
  
  outbytes_remaining = outbuf_size - 1; /* -1 for nul */
  outp = dest = g_malloc (outbuf_size);

 again:
  
  err = g_iconv (cd, (char **)&p, &inbytes_remaining, &outp, &outbytes_remaining);

  if (err == (size_t) -1)
    {
      switch (errno)
	{
	case EINVAL:
	  /* Incomplete text, do not report an error */
	  break;
	case E2BIG:
	  {
	    size_t used = outp - dest;

	    /* glibc's iconv can return E2BIG even if there is space
	     * remaining if an internal buffer is exhausted. The
	     * folllowing is a heuristic to catch this. The 16 is
	     * pretty arbitrary.
	     */
	    if (used + 16 > outbuf_size)
	      {
		outbuf_size = (outbuf_size - 1) * 2 + 1;
		dest = g_realloc (dest, outbuf_size);
		
		outp = dest + used;
		outbytes_remaining = outbuf_size - used - 1; /* -1 for nul */
	      }

	    goto again;
	  }
	case EILSEQ:
	  g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
		       _("Invalid byte sequence in conversion input"));
	  have_error = TRUE;
	  break;
	default:
	  g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_FAILED,
		       _("Error during conversion: %s"),
		       strerror (errno));
	  have_error = TRUE;
	  break;
	}
    }

  *outp = '\0';
  
  g_iconv_close (cd);

  if (bytes_read)
    *bytes_read = p - str;
  else
    {
      if ((p - str) != len) 
	{
	  g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_PARTIAL_INPUT,
		       _("Partial character sequence at end of input"));
	  have_error = TRUE;
	}
    }

  if (bytes_written)
    *bytes_written = outp - dest;	/* Doesn't include '\0' */

  if (have_error)
    {
      g_free (dest);
      return NULL;
    }
  else
    return dest;
}

/**
 * g_convert_with_fallback:
 * @str:          the string to convert
 * @len:          the length of the string
 * @to_codeset:   name of character set into which to convert @str
 * @from_codeset: character set of @str.
 * @fallback:     UTF-8 string to use in place of character not
 *                present in the target encoding. (This must be
 *                in the target encoding), if %NULL, characters
 *                not in the target encoding will be represented
 *                as Unicode escapes \x{XXXX} or \x{XXXXXX}.
 * @bytes_read:   location to store the number of bytes in the
 *                input string that were successfully converted, or %NULL.
 *                Even if the conversion was succesful, this may be 
 *                less than len if there were partial characters
 *                at the end of the input. If the error
 *                G_CONVERT_ERROR_ILLEGAL_SEQUENCE occurs, the value
 *                stored will the byte fofset after the last valid
 *                input sequence.
 * @bytes_written: the stored in the output buffer (not including the
 *                 terminating nul.
 * @error:        location to store the error occuring, or %NULL to ignore
 *                errors. Any of the errors in #GConvertError may occur.
 *
 * Convert a string from one character set to another, possibly
 * including fallback sequences for characters not representable
 * in the output. Note that it is not guaranteed that the specification
 * for the fallback sequences in @fallback will be honored. Some
 * systems may do a approximate conversion from @from_codeset
 * to @to_codeset in their iconv() functions, in which case GLib
 * will simply return that approximate conversion.
 *
 * Return value: If the conversion was successful, a newly allocated
 *               NUL-terminated string, which must be freed with
 *               g_free. Otherwise %NULL and @error will be set.
 **/
gchar*
g_convert_with_fallback (const gchar *str,
			 gint         len,
			 const gchar *to_codeset,
			 const gchar *from_codeset,
			 gchar       *fallback,
			 gint        *bytes_read,
			 gint        *bytes_written,
			 GError     **error)
{
  gchar *utf8;
  gchar *dest;
  gchar *outp;
  const gchar *insert_str = NULL;
  const gchar *p;
  int inbytes_remaining;
  const gchar *save_p = NULL;
  size_t save_inbytes = 0;
  size_t outbytes_remaining;
  size_t err;
  GIConv cd;
  size_t outbuf_size;
  gboolean have_error = FALSE;
  gboolean done = FALSE;

  GError *local_error = NULL;
  
  g_return_val_if_fail (str != NULL, NULL);
  g_return_val_if_fail (to_codeset != NULL, NULL);
  g_return_val_if_fail (from_codeset != NULL, NULL);
     
  if (len < 0)
    len = strlen (str);
  
  /* Try an exact conversion; we only proceed if this fails
   * due to an illegal sequence in the input string.
   */
  dest = g_convert (str, len, to_codeset, from_codeset, 
		    bytes_read, bytes_written, &local_error);
  if (!local_error)
    return dest;

  if (!g_error_matches (local_error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE))
    {
      g_propagate_error (error, local_error);
      return NULL;
    }
  else
    g_error_free (local_error);

  /* No go; to proceed, we need a converter from "UTF-8" to
   * to_codeset, and the string as UTF-8.
   */
  cd = open_converter (to_codeset, "UTF-8", error);
  if (cd == (GIConv) -1)
    {
      if (bytes_read)
        *bytes_read = 0;
      
      if (bytes_written)
        *bytes_written = 0;
      
      return NULL;
    }

  utf8 = g_convert (str, len, "UTF-8", from_codeset, 
		    bytes_read, &inbytes_remaining, error);
  if (!utf8)
    return NULL;

  /* Now the heart of the code. We loop through the UTF-8 string, and
   * whenever we hit an offending character, we form fallback, convert
   * the fallback to the target codeset, and then go back to
   * converting the original string after finishing with the fallback.
   *
   * The variables save_p and save_inbytes store the input state
   * for the original string while we are converting the fallback
   */
  p = utf8;
  /* Due to a GLIBC bug, round outbuf_size up to a multiple of 4 */
  /* + 1 for nul in case len == 1 */
  outbuf_size = ((len + 3) & ~3) + 1;
  outbytes_remaining = outbuf_size - 1; /* -1 for nul */
  outp = dest = g_malloc (outbuf_size);

  while (!done && !have_error)
    {
      size_t inbytes_tmp = inbytes_remaining;
      err = g_iconv (cd, (char **)&p, &inbytes_tmp, &outp, &outbytes_remaining);
      inbytes_remaining = inbytes_tmp;

      if (err == (size_t) -1)
	{
	  switch (errno)
	    {
	    case EINVAL:
	      g_assert_not_reached();
	      break;
	    case E2BIG:
	      {
		size_t used = outp - dest;

		/* glibc's iconv can return E2BIG even if there is space
		 * remaining if an internal buffer is exhausted. The
		 * folllowing is a heuristic to catch this. The 16 is
		 * pretty arbitrary.
		 */
		if (used + 16 > outbuf_size)
		  {
		    outbuf_size = (outbuf_size - 1) * 2 + 1;
		    dest = g_realloc (dest, outbuf_size);
		    
		    outp = dest + used;
		    outbytes_remaining = outbuf_size - used - 1; /* -1 for nul */
		  }
		
		break;
	      }
	    case EILSEQ:
	      if (save_p)
		{
		  /* Error converting fallback string - fatal
		   */
		  g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
			       _("Cannot convert fallback '%s' to codeset '%s'"),
			       insert_str, to_codeset);
		  have_error = TRUE;
		  break;
		}
	      else
		{
		  if (!fallback)
		    { 
		      gunichar ch = g_utf8_get_char (p);
		      insert_str = g_strdup_printf ("\\x{%0*X}",
						    (ch < 0x10000) ? 4 : 6,
						    ch);
		    }
		  else
		    insert_str = fallback;
		  
		  save_p = g_utf8_next_char (p);
		  save_inbytes = inbytes_remaining - (save_p - p);
		  p = insert_str;
		  inbytes_remaining = strlen (p);
		}
	      break;
	    default:
	      g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_FAILED,
			   _("Error during conversion: %s"),
			   strerror (errno));
	      have_error = TRUE;
	      break;
	    }
	}
      else
	{
	  if (save_p)
	    {
	      if (!fallback)
		g_free ((gchar *)insert_str);
	      p = save_p;
	      inbytes_remaining = save_inbytes;
	      save_p = NULL;
	    }
	  else
	    done = TRUE;
	}
    }

  /* Cleanup
   */
  *outp = '\0';
  
  g_iconv_close (cd);

  if (bytes_written)
    *bytes_written = outp - str;	/* Doesn't include '\0' */

  g_free (utf8);

  if (have_error)
    {
      if (save_p && !fallback)
	g_free ((gchar *)insert_str);
      g_free (dest);
      return NULL;
    }
  else
    return dest;
}

/*
 * g_locale_to_utf8
 *
 * 
 */

/**
 * g_locale_to_utf8:
 * @opsysstring:   a string in the encoding of the current locale
 * @len:           the length of the string, or -1 if the string is
 *                 NULL-terminated.
 * @bytes_read:    location to store the number of bytes in the
 *                 input string that were successfully converted, or %NULL.
 *                 Even if the conversion was succesful, this may be 
 *                 less than len if there were partial characters
 *                 at the end of the input. If the error
 *                 G_CONVERT_ERROR_ILLEGAL_SEQUENCE occurs, the value
 *                 stored will the byte fofset after the last valid
 *                 input sequence.
 * @bytes_written: the stored in the output buffer (not including the
 *                 terminating nul.
 * @error: location to store the error occuring, or %NULL to ignore
 *                 errors. Any of the errors in #GConvertError may occur.
 * 
 * Converts a string which is in the encoding used for strings by
 * the C runtime (usually the same as that used by the operating
 * system) in the current locale into a UTF-8 string.
 * 
 * Return value: The converted string, or %NULL on an error.
 **/
gchar *
g_locale_to_utf8 (const gchar  *opsysstring,
		  gint          len,
		  gint         *bytes_read,
		  gint         *bytes_written,
		  GError      **error)
{
#ifdef G_OS_WIN32

  gint i, clen, total_len, wclen, first;
  wchar_t *wcs, wc;
  gchar *result, *bp;
  const wchar_t *wcp;

  if (len == -1)
    len = strlen (opsysstring);
  
  wcs = g_new (wchar_t, len);
  wclen = MultiByteToWideChar (CP_ACP, 0, opsysstring, len, wcs, len);

  wcp = wcs;
  total_len = 0;
  for (i = 0; i < wclen; i++)
    {
      wc = *wcp++;

      if (wc < 0x80)
	total_len += 1;
      else if (wc < 0x800)
	total_len += 2;
      else if (wc < 0x10000)
	total_len += 3;
      else if (wc < 0x200000)
	total_len += 4;
      else if (wc < 0x4000000)
	total_len += 5;
      else
	total_len += 6;
    }

  result = g_malloc (total_len + 1);
  
  wcp = wcs;
  bp = result;
  for (i = 0; i < wclen; i++)
    {
      wc = *wcp++;

      if (wc < 0x80)
	{
	  first = 0;
	  clen = 1;
	}
      else if (wc < 0x800)
	{
	  first = 0xc0;
	  clen = 2;
	}
      else if (wc < 0x10000)
	{
	  first = 0xe0;
	  clen = 3;
	}
      else if (wc < 0x200000)
	{
	  first = 0xf0;
	  clen = 4;
	}
      else if (wc < 0x4000000)
	{
	  first = 0xf8;
	  clen = 5;
	}
      else
	{
	  first = 0xfc;
	  clen = 6;
	}
      
      /* Woo-hoo! */
      switch (clen)
	{
	case 6: bp[5] = (wc & 0x3f) | 0x80; wc >>= 6; /* Fall through */
	case 5: bp[4] = (wc & 0x3f) | 0x80; wc >>= 6; /* Fall through */
	case 4: bp[3] = (wc & 0x3f) | 0x80; wc >>= 6; /* Fall through */
	case 3: bp[2] = (wc & 0x3f) | 0x80; wc >>= 6; /* Fall through */
	case 2: bp[1] = (wc & 0x3f) | 0x80; wc >>= 6; /* Fall through */
	case 1: bp[0] = wc | first;
	}

      bp += clen;
    }
  *bp = 0;

  g_free (wcs);

  if (bytes_read)
    *bytes_read = len;
  if (bytes_written)
    *bytes_written = total_len;
  
  return result;

#else

  char *charset, *str;

  if (g_get_charset (&charset))
    return g_strdup (opsysstring);

  str = g_convert (opsysstring, len, 
		   "UTF-8", charset, bytes_read, bytes_written, error);
  
  return str;
#endif
}

/**
 * g_locale_from_utf8:
 * @utf8string:    a UTF-8 encoded string 
 * @len:           the length of the string, or -1 if the string is
 *                 NULL-terminated.
 * @bytes_read:    location to store the number of bytes in the
 *                 input string that were successfully converted, or %NULL.
 *                 Even if the conversion was succesful, this may be 
 *                 less than len if there were partial characters
 *                 at the end of the input. If the error
 *                 G_CONVERT_ERROR_ILLEGAL_SEQUENCE occurs, the value
 *                 stored will the byte fofset after the last valid
 *                 input sequence.
 * @bytes_written: the stored in the output buffer (not including the
 *                 terminating nul.
 * @error: location to store the error occuring, or %NULL to ignore
 *                 errors. Any of the errors in #GConvertError may occur.
 * 
 * Converts a string from UTF-8 to the encoding used for strings by
 * the C runtime (usually the same as that used by the operating
 * system) in the current locale.
 * 
 * Return value: The converted string, or %NULL on an error.
 **/
gchar *
g_locale_from_utf8 (const gchar *utf8string,
		    gint         len,
		    gint        *bytes_read,
		    gint        *bytes_written,
		    GError     **error)
{
#ifdef G_OS_WIN32

  gint i, mask, clen, mblen;
  wchar_t *wcs, *wcp;
  gchar *result;
  guchar *cp, *end, c;
  gint n;
  
  if (len == -1)
    len = strlen (utf8string);
  
  /* First convert to wide chars */
  cp = (guchar *) utf8string;
  end = cp + len;
  n = 0;
  wcs = g_new (wchar_t, len + 1);
  wcp = wcs;
  while (cp != end)
    {
      mask = 0;
      c = *cp;

      if (c < 0x80)
	{
	  clen = 1;
	  mask = 0x7f;
	}
      else if ((c & 0xe0) == 0xc0)
	{
	  clen = 2;
	  mask = 0x1f;
	}
      else if ((c & 0xf0) == 0xe0)
	{
	  clen = 3;
	  mask = 0x0f;
	}
      else if ((c & 0xf8) == 0xf0)
	{
	  clen = 4;
	  mask = 0x07;
	}
      else if ((c & 0xfc) == 0xf8)
	{
	  clen = 5;
	  mask = 0x03;
	}
      else if ((c & 0xfc) == 0xfc)
	{
	  clen = 6;
	  mask = 0x01;
	}
      else
	{
	  g_free (wcs);
	  return NULL;
	}

      if (cp + clen > end)
	{
	  g_free (wcs);
	  return NULL;
	}

      *wcp = (cp[0] & mask);
      for (i = 1; i < clen; i++)
	{
	  if ((cp[i] & 0xc0) != 0x80)
	    {
	      g_free (wcs);
	      return NULL;
	    }
	  *wcp <<= 6;
	  *wcp |= (cp[i] & 0x3f);
	}

      cp += clen;
      wcp++;
      n++;
    }
  if (cp != end)
    {
      g_free (wcs);
      return NULL;
    }

  /* n is the number of wide chars constructed */

  /* Convert to a string in the current ANSI codepage */

  result = g_new (gchar, 3 * n + 1);
  mblen = WideCharToMultiByte (CP_ACP, 0, wcs, n, result, 3*n, NULL, NULL);
  result[mblen] = 0;
  g_free (wcs);

  if (bytes_read)
    *bytes_read = len;
  if (bytes_written)
    *bytes_written = mblen;
  
  return result;

#else

  gchar *charset, *str;

  if (g_get_charset (&charset))
    return g_strdup (utf8string);

  str = g_convert (utf8string, strlen (utf8string), 
		   charset, "UTF-8", bytes_read, bytes_written, error);

  return str;
  
#endif
}

/**
 * g_filename_to_utf8:
 * @opsysstring:   a string in the encoding for filenames
 * @len:           the length of the string, or -1 if the string is
 *                 NULL-terminated.
 * @bytes_read:    location to store the number of bytes in the
 *                 input string that were successfully converted, or %NULL.
 *                 Even if the conversion was succesful, this may be 
 *                 less than len if there were partial characters
 *                 at the end of the input. If the error
 *                 G_CONVERT_ERROR_ILLEGAL_SEQUENCE occurs, the value
 *                 stored will the byte fofset after the last valid
 *                 input sequence.
 * @bytes_written: the stored in the output buffer (not including the
 *                 terminating nul.
 * @error: location to store the error occuring, or %NULL to ignore
 *                 errors. Any of the errors in #GConvertError may occur.
 * 
 * Converts a string which is in the encoding used for filenames
 * into a UTF-8 string.
 * 
 * Return value: The converted string, or %NULL on an error.
 **/
gchar*
g_filename_to_utf8 (const gchar *opsysstring, 
		    gint         len,
		    gint        *bytes_read,
		    gint        *bytes_written,
		    GError     **error)
{
#ifdef G_OS_WIN32
  return g_locale_to_utf8 (opsysstring, len,
			   bytes_read, bytes_written,
			   error);
#else
  if (getenv ("G_BROKEN_FILENAMES"))
    return g_locale_to_utf8 (opsysstring, len,
			     bytes_read, bytes_written,
			     error);

  if (bytes_read || bytes_written)
    {
      gint len = strlen (opsysstring);

      if (bytes_read)
	*bytes_read = len;
      if (bytes_written)
	*bytes_written = len;
    }
  
  if (len < 0)
    return g_strdup (opsysstring);
  else
    return g_strndup (opsysstring, len);
#endif
}

/**
 * g_filename_from_utf8:
 * @utf8string:    a UTF-8 encoded string 
 * @len:           the length of the string, or -1 if the string is
 *                 NULL-terminated.
 * @bytes_read:    location to store the number of bytes in the
 *                 input string that were successfully converted, or %NULL.
 *                 Even if the conversion was succesful, this may be 
 *                 less than len if there were partial characters
 *                 at the end of the input. If the error
 *                 G_CONVERT_ERROR_ILLEGAL_SEQUENCE occurs, the value
 *                 stored will the byte fofset after the last valid
 *                 input sequence.
 * @bytes_written: the stored in the output buffer (not including the
 *                 terminating nul.
 * @error: location to store the error occuring, or %NULL to ignore
 *                 errors. Any of the errors in #GConvertError may occur.
 * 
 * Converts a string from UTF-8 to the encoding used for filenames.
 * 
 * Return value: The converted string, or %NULL on an error.
 **/
gchar*
g_filename_from_utf8 (const gchar *utf8string,
		      gint         len,
		      gint        *bytes_read,
		      gint        *bytes_written,
		      GError     **error)
{
#ifdef G_OS_WIN32
  return g_locale_from_utf8 (utf8string, len,
			     bytes_read, bytes_written,
			     error);
#else
  if (getenv ("G_BROKEN_FILENAMES"))
    return g_locale_from_utf8 (utf8string, len,
			       bytes_read, bytes_written,
			       error);

  if (bytes_read || bytes_written)
    {
      gint len = strlen (utf8string);

      if (bytes_read)
	*bytes_read = len;
      if (bytes_written)
	*bytes_written = len;
    }

  if (len < 0)
    return g_strdup (utf8string);
  else
    return g_strndup (utf8string, len);
#endif
}